Given that the Sigma was tested on a 22 MP body and the Tokina on a 18 MP body, the resolution numbers (ie, the P-Mpix ratings) are not directly comparable. If you scale them with the ratio of number of MP (22.12/17.92 = 1.235), ie, 9 * 1.235 = 11.1, both lenses resolve the same number of 'MP' (as defined by DxO).You can also look at more bodies where these lenses were tested on and compare how much Mpix per MP they get: Sigma on 5D 8 (12) vs. Tokina on 40D 6 (10), or Sigma on 1DsIII 9 (21) - Tokina 7 (15). Overall, given the same amount of MP on the sensor behind both lenses, both lenses achieve about the same final resolution.

so worst case scenario the Sigma gives you the same resolution as the tokina but is cheaper. right?

Thus, for this lens pair, your premise of bigger (image circle) = better (resolution) evidently does not apply and your statement about the Sigma having "much more detail" was not proven to be correct.

bigger (image circle) = better (resolution) is only one attribute makes FF images sharper, there are obviously other attributes at play. you are taking things out of context by holding it to be an absolute rule.